Newtrons are based on chameleons. Newtrons have a head, a stripy tail and four white feet with three fingers. One of these fingers are backwards so the Newtrons can get an extra grip. They also have yellow eyes with small pupils and a brown and sharp parietal crest. Newtrons come in two color varieties: green and blue. The green variation has yellow eyes and the blue varitation has red eyes.
Newtrons can camouflage themselves accordingly to the wall they are on and phase out of sight when they see their target. They have also different methods of attack depending on their colors:
The green Newtron, after becoming visible, spits a ball of energy at the player before turning invisible again. It never moves from its wall though.
The blue Newtron, after becoming visible, drops from the wall and morphs into a chameleon-shaped rocket, which chases Sonic in a fixed horizontal line. The blue variety is easier to deal with as it can be attacked, unlike most of its green counterparts. Green Newtrons in Sonic the Hedgehog 4: Episode I however, are also able turn into rockets as well.
Sonic the Hedgehog (1991)
Newtrons make their first appearance in the original 16-bit version of Sonic the Hedgehog. Both varieties appear in the Green Hill Zone. Both of them can be destroyed with Spin Jump as they starts to appear on the wall. Green variants can shoot energy balls from the walls at Sonic, whereas blue variants will jump off the walls and attack the player directly. On some occasions, the player is unable to destroy green Newtrons depending on their placement in the Zone.
In 8-bit version of the game with same name, only the green variation of Newtrons appear at Jungle Zone, although they have the same attack patterns as their 16-bit counterpart. However Newtrons do not have Animals inside of them as power source like many other Badniks in the Master System and Game Gear titles.
Sonic the Hedgehog 2 (8-bit)
In the 8-bit version of Sonic the Hedgehog 2, the Newtron are known as Meleons (メレオン,Meleons?) in the Japanese manual. In this game, the Newtrons appear in Under Ground Zone, Sky High Zone and Green Hills Zone. This game also has the two variations of Newtrons, although the green ones have the same color scheme as the rocket-types. Both types have the same attack patterns from previous game, although none of them contain Animals.
Sonic the Hedgehog 4
In Sonic the Hedgehog 4: Episode I, only the green variety of Newtrons appears in Splash Hill Zone. They keep their attack pattern from their first game and can also transforms themselves into a rocket which moves in a horizontal direction along the platforms.
In the Nintendo 3DS version of Sonic Generations, both blue and green Newtrons appear in Green Hill Act 1. Despite their redesign for the game, the Newtrons have the same attack pattern as in their first game and are placed in the exact same places. However, none of Newtrons contain Animals.
Sonic Lost World
In Sonic Lost World, the Newtrons regain their original design, although they are smaller. During the game, it turns out that the Badniks, the Newtrons included, got hijacked by the Deadly Six.
In the Sonic the Comic series published by Fleetway Editions, the Newtrons were standard models in Dr. Robotnik's Badnik army. In this media, they lacked any form of projectile weapons and cloaking ability, and were more akin to melee fighters. Depending on the artist, the Newtrons' design would differ between issues. Earlier models of Newtrons were also quadruped, but later models became bipedal.
The Newtrons got decommissioned after the occurrence of an electromagnetic pulse which affected the planet Mobius.
The toy company TOMY has released Newtron action figurine during the release of Sonic & Knuckles as it also includes a series of 21 Sonic figurines and these figurines came in packs of four under the Sonic & Knuckles label and were also released individually under a Sonic the Hedgehog label.